feat(frontends/lean/pp_options): use a more effective get_distinguishing_pp_options

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(doc/authors.md): update authors.md page

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
feat(kernel/conveter): improve support for proof irrelevant in the converter

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
chore(README.md): remove link to Lean 0.1

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(doc/lean/tutorial): typos

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
fix(doc/lean/tutorial): typos